1) Field of the Invention
The invention relates generally to the field of flow cytometry. More particularly, the invention relates to methods and systems for studying a fluid channeled within a passageway intersecting the light guided in an optical fiber.
2) Description of the Prior Art
Many techniques exist to study the presence, the quantity, the size or the vitality status (alive or dead) of bacteria or of other small bodies. For example, the number of bacteria may be determined by counting them in a Petri dish, using a microscope counting technique, via the chain reaction of polymerase, and using flow cytometry. Flow cytometry is a technique which allows one to analyze and to sort small bodies like cells, bacteria and other particles in a fluid medium. In flow cytometers of the prior art, a fluid containing the small bodies is circulated within a transparent tube, and a laser is aimed at the tube. The laser light, after having crossed the tube, is received and analyzed, which gives information about the particles flowing within the tube. Several parameters of the particles may be studied simultaneously (the nature of the particle, the dimension of the particle, etc.) by marking the particles to be analyzed with dyes and measuring the fluorescence emitted by those dyed particles and by analyzing the intensity of the transmitted laser light beam after it has interacted with the fluid. All of the above techniques require the intervention of a skilled technician. In particular, in the case of the prior art flow cytometry techniques, a skilled technician must adjust and precisely align the laser beam so that the laser beam may efficiently interact with the particles flowing into the tube.
Known flow cytometers are described, for example, in U.S. Pat. Nos. 4,667,830; 5,464,581; 5,483,469; 5,602,039; 5,643,796; 5,700,692; 6,713,019 and 6,793,642. The flow cytometers, such as described in the patents cited above, usually employ lasers as the light source. Although lasers are generally effective in producing focused beams which are of sufficient intensity to excite the particles of interest to provide detectable fluorescence, the use of lasers can have some drawbacks. For example, the types of lasers employed in many known flow cytometers are very expensive, and thus increase the overall cost of the system. Also, because the lasers emit very high intensity light, stray light from the laser beam can interfere with the fluorescent light emanating from the particles of interest, thus adversely affecting fluorescence measurements. Therefore, a need exists for an improved system to obtain more accurate measurements while also decreasing the overall size and cost of the apparatus.